Control system



Nov. 9, 1937.

H. HOOTZ CONTROL SYSTEM Filed July 1, 1956 Inventor- Herbert, Hootz,

. I has ALNor'ne- Patented Nov. 9, 1937 n CONTROL SYSTEM Herbert Hootz, Berlin, Germany, assignor to General Electricicompany, a corporation of New York Application July 1, 1936, Serial No. 88,435 In Germany July 9, 1935 3 Claims. (Cl. 172 -179) This invention relates to control systems, more the supply lines H. A pair of reversing switches particularly to systems for controlling the opera- I2, l3 are provided for connecting the motor ill to tion of electric motors, and it has for an object the the supply source for operation in either the forprovision of a simple, reliable and improved conward or reverse direction and a multi-position 5 trol system of this character. master switch I is provided for controlling the Trolley motion gear and especially crane luifing operation of the reversing contactors I2, Hi. This gear driven by electric motors require a very senmaster switch is illustrated conventionally as a sitive control if troublesome load oscillation is to reversing type drum switch. Switches of this be avoided. A control provided for this purpose type may be and usually are provided with fingers l0 usually has a simple symmetrical multi-position and cooperating segments for controlling sections motor switch which is arranged to provide reverse of resistance in the motor circuit thereby to concurrentbraking in the first position. When actutrol its speed. Such master switches and the sting such a master switch through the zero posiwiring therefor are often very complicated and tion, in which position the drive can coast, the accordingly all features not facilitating an undermechanical brake is held released by means of a standing of the invention have been omitted in 15 special auxiliary switch, and an additional resistthe interest of simplicity. ance is also inserted. in the rotor circuit for the Motor [0 is provided with a mechanical brake smooth braking. Furthermore, with such a conl5 comprising a drum l 5a connected to the motor trol the master switch handle must be operated shaft and a pair of brake shoes normally biased 2 through a wide arc and also must be actuated to braking position by means of a spring I6. t ou the p notch at the zero Pos eaeh An electro-hydraulic operating mechanism l l is time the motor is plugged. provided for releasing the brake against the bias Such an arrangement has the further dlsadof the spring. This operator comprises a cylinder vantage that when using the connection for luifing containing a fluid such as oil, a movable piston of Cranes in c Of an Overhauling tiv connected by means of connecting rod l8 to the 25 load imme i ly the motor s r e a v ry brake shoe actuating arm l9, and an electric sudde acc a immediately occurs which motor 20 which drives an impeller within the causes the load to oscillate. I container to produce a pressure for moving the An object of the invention is to eliminate these piston. A switching device 2| is provided for disadvantages by providing for plugging without connecting the motor 20 of the electro-hydraulic 30 a t t the master Switch hrough the zero operating mechanism to the source II or to the P05115101! end by affording the same switching possecondary winding of motor l0, depending upon sibilities at each side of the master'switch without the position of the master switch M. This switch adding to its complexity. This is accomplished comprises a cam 2h connected with or forming a y arranging the control to Provide r P pel part of the master switch I, and a movable con- 35 actuation of the mechanical brake for smooth tact member 2'1: carrying a cam rider 2 '0 in starting operation on the first point of the master engagement with the cam. When the master switch in the running direction and by the proswitch H is in the oil position or the first position vision of an auxiliary switching device to provide either forward or reverse, the switch 2| is in its 4.) low torque operation O the driving motel up n lower position in which it connects the motor 20 4 returning the master Switch from the ast P05 to the slip rings of motor in through transformer tion to the second position and reverse current- 22 and when the master switch It is in any other braking or plugging on the first position. position, either forward or reverse, the switch 2i For a better and more complete understanding is in its upper position in which it connects motor of the invention reference should now be had to 20 to the source I I through master switch l4.

the i )llowing specification and to the accompany- An auxiliary switching device, illustrated as a ing d awing, the single figure of which is a simple manually operated push button type switch 23 is diagrammatical representation of an embodiment provided for establishing plugging connections of the invention. for motor 10 in the first position on either side of Referring now to the drawing, an electric motor master switch l4, without operating the master III is connected to a load (not shown) such for switch through the zero position. example as the trolley motion gear or lufling gear With the foregoing understanding of the invenof a crane. This motor is illustrated as an altertion, the operation of the system will readily be nating current wound rotor induction motor and understood from the following description: is supplied from a suitable source represented by The apparatus is illustrated in its normally de- 55 duction' motor, a mechanical brake for said'motor biased to the braking position, a mnltiposition master switch for controlling the operation of said motor, an electro-hydraulic operating mechanism for releasing said brake, said mechanism having an electric driving motor, means operable in the first running position of said master switch for connecting the motor of said operating mechanism to the slip rings of said induction motor thereby to produce a graduated braking action proportional to the speed of said induction motor and responsive to operation oi said master switch to a position beyond said first running position for connecting the motor of said electro-hydraulic operating mechanism to said source to eflect full release of said brake, and an auxiliary switching device operable upon return of said master switch for disconnecting said induction motor from said source and operable upon return of said master switch to said first position for establishing plugging braking connections for said induction motor.

3. A motor control system comprising in combination, a source of alternating voltage, an alternating current induction motor, a mechanical ls brake for said motor biased to the braking position, a mnltiposition reversing master switch for controlling the direction of operation of said motor, an electro-hydraulic operating mechanism for said brake having an alternating current driving motor, means operable in the first running position 01' either the forward or reverse side of said master switch for connecting the motor of said electro-hydraullc braking mechanism to the slip rings of said induction motor to provide a graduated braking force proportional to the speed oi said induction motor and responsive to operation of said master switch to a running position beyond the first position for connecting the motor said electro-hydraulic operating mechanism to said source for eifecting complete release of the brake, and an auxiliary switching device operable during return of said master switch toward zero podtion from a running position in either direction for disconnecting said induction motor from said source and operable upon return of said master switch to the first running position for establishing plugging braking connections for said motor.

HERBERT 110012. 

